Now I haven’t researched this too closely, but I haven't heard any mention that Apple is doing this with iPads in addition to the iPhones (6, 6s, SE, and 7) they specifically mentioned. Or that it slows down devices while they are plugged in, etc.

Regardless, easier and more cost efficient battery replacements would mitigate the issue. (Apparently they don’t blanket slow down older phones: they slow down older phones with gimpy batteries, so replacing the battery turns the slowdown ‘feature’ off).

Again, this seems like an iPhone only thing, but Apple is responding to the anger by reducing the cost of iPhone battery replacements in 2018 to around $30. I’ll happily take advantage of that for my iPhone 6s plus next fall.